The present invention relates to methods, compositions, and kits for generating conjugated gold nanoparticles. In certain embodiments, the present invention provides methods of generating unsaturated conjugated gold nanoparticles by mixing naked gold nanoparticles with a first type of attachment molecules at a molar ratio such that the attachment molecules attach to the naked gold particles at a density level below the saturation level of the naked gold particles (e.g., at a saturation level of 1-99%). In some embodiments, a second type of attachment molecules (e.g., with the opposite charge as the first type of attachment molecules) are mixed with the unsaturated conjugated gold nanoparticles to generate double-conjugated gold nanoparticles (e.g., that are zwitterionic).